1. Field of the Invention
The present invention relates to a single-layered structure excellent in fuel barrier properties and a multi-layered shaped article having at least one layer made of the single-layered structure, more particularly, relates to a single-layered structure having a low fuel permeability and an excellent heat resistance which is particularly suitable for the production of containers of alcohol-containing fuels, tubes and parts, and relates to a multi-layered shaped article including at least one layer made of such a single-layered structure.
2. Description of the Prior Art
In view of lightweight, needlessness of anti-corrosive treatment, wide design liberty, reduction in the number of processing steps, and capability of full automatic production, resin containers formed by blow molding, etc. have come to attract attention as the fuel storage containers and the replacement of metal fuel containers by resin fuel containers is now advancing.
However, since polyethylene (high density polyethylene) hitherto used for resin fuel containers is poor in the fuel barrier properties despite its excellence in mechanical strength, moldability and economy, the fuel containers made of polyethylene cannot meet the recent regulations of fuel permeation from fuel container.
To solve this problem, many proposals have been made on the prevention of the fuel permeation, for example, by a fluorine treatment of the inner surface of containers or a blending of polyamide resin to polyethylene (JP 55-121017A, JP 5-156036A and JP 10-279752). However, the fluorine treatment is now scarcely used because the use of harmful gas requires safety precautions for its handling and troublesome recovery of the harmful gas after treatment. By blending a barrier resin into polyolefin so as to disperse throughout polyethylene in laminar, the fuel permeation can be reduced to some extent. However, the fuel barrier properties are sill unsatisfactory. If the addition amount of the barrier resin is increased, other problems are caused, for example, the absorption ability of crash impact is reduced and the moldability becomes poor, thereby failing to fully meet the regulations which are getting increasingly stringent. The use of alcohols such as ethanol as a fuel has been progressively considered because the use of fossil fuels can be reduced by adding alcohols into gasoline thereby to reduce the carbon dioxide emission. However, since known barrier resins such as nylon 6 and ethylene-vinyl alcohol copolymers show poor barrier properties against alcohols, a material having an enhanced barrier properties is demanded.